Where is the microtubule located in the cell

They're made up of these triplets of microtubules. So each one of these triplets are three microtubules that are attached to each other, and there are nine of these triplets that make up one centriole.

So I'm just gonna circle them. Eight and nine, so that means it takes 27 microtubules to make one centriole, and what purpose do these centrioles serve? Well, when a cell is replicating, or undergoing mitosis, these centrioles are going to duplicate, and a pair of centrioles will land up on either side of the cell, and we're gonna fast forward to the metaphase part of mitosis right now.

So here we are, in the metaphase part of mitosis, and we're looking all what's called the mitotic spindle. The blue lines that kind of look, maybe like I don't know the web of a spider.

So those are all microtubule fibers, and they're holding on to the chromosomes in a very specific way. So, let's go through this mitotic spindle step by step. So we have in the center of the cell, the chromosomes.

Then at the center of the chromosomes in that magenta, that's the centromere, and then outside of the centromere in light blue, that is the kinetichore. The kinetichore is a protein on the chromosome that's gonna serve as an anchoring site for the fibers. So, coming out of the kinetichore, those blue little fibers, those are the kinetichore fibers, and then the kinetichore fibers turn into the microtubules.

So, let's pick one right over here. So these are the microtubules, and if I wanted to be more specific I'd say that these are the interpolar microtubules. So I'm just going to point out a couple more to make it clear.

This would be an interpolar microtubule, this would be an interpolar microtubule, this would be not an interpolar microtubule. We'll see in a minute what that is. But anyway, they're called interpolar microtubules because they are between the two poles of the cell, this being one pole, and this being another pole, and you can see, the interpolar microtubules are attached to our centrioles.

I'm just gonna highlight them to make it more clear. Here's one pair of centrioles, and here's another pair of centrioles.

So the centrioles are an anchoring site for the interpolar microtubules. Let's just go through a couple of other structures.

So, these microtubules that are kind of coming out of the centrioles, those are called astral microtubules, and they're called astral microtubules because this part, the centrioles plus those fibers that are kinda coming out of it. So, each one of these is called an aster, and it's called an aster because it forms a shape that looks something like a star, and the word aster means star, and you can see some of the interpolar microtubules are actually attached to the astral microtubule.

That's a pretty complex network going on. But, what's the point of this entire mitotic spindle? Well, if you recall, I mentioned before that microtubules can shorten or become longer very, very quickly.

So what's going to happen during the next phase of mitosis, during anaphase, is the microtubules are going to become shorter and pull the chromosomes apart so that one half of all the chromosomes ends up on one side of the cell, and the other half of all the chromosomes ends up on the other side of the cell.

So it helps to separate the chromosomes, and then eventually this cell is gonna be split down the middle, and two different cells are going to be formed. So the purpose of the centrioles is they serve as an anchoring site for the microtubules that are attached to the chromosomes, and then the microtubules will become shorter pulling the chromosomes apart having half of them in one half of the cell, the other half in the other half of the cell.

So, let's just recap. We mentioned that there are two different types of microtubule organizing centers. We said the first was the centrosome. Microtubules are continuously being assembled and disassembled so that tubulin monomers can be transported elsewhere to build microtubules when needed. Presented in Figure 2 is a digital image of the microtubule network found in an embryonic mouse cell as seen through a fluorescence optical microscope.

The extensive intertwined network is labeled with primary antibodies to alpha -tubulin, which are then stained with secondary antibodies containing a green fluorescent dye. The nucleus was counterstained with a red dye to note its location in relation to the microtubule network. Fluorescence microscopy is an important tool that scientists use to examine the structure and function of internal cellular organelles.

In addition to their structural support role, microtubules also serve as a highway system along which organelles can be transported with the aid of motor proteins. For instance, the microtubule network interconnects the Golgi apparatus with the plasma membrane to guide secretory vesicles for export, and also transports mitochondria back and forth in the cytoplasm.

Another example is the translocation of vesicles containing neurotransmitters by microtubules to the tips of nerve cell axons. The motor proteins involved in organelle transport operate by altering their three-dimensional conformation using adenosine triphosphate ATP as fuel to move back and forth along a microtubule.

With each step, the motor molecule releases one portion of the microtubule and grips a second site farther long the filament. Motor proteins, which are grouped into several distinct classes, attach to organelles through specialized receptors. Since eukaryotic cells greatly depend upon the integrity of microtubules and other cytoskeletal filaments to maintain their structure and essentially to survive, many plants produce natural toxins aimed at disrupting the microtubule network as a means of self-defense.

Taxol , for example, is a toxic substance produced by a species of yew trees that increases microtubule polymerization building a macromolecule by binding to the filament and stabilizing it. Other natural toxins, such as the colchicine produced by the meadow saffron, destabilize microtubules and hinder their polymerization.

Both kinds of events can be fatal to the affected cell, though in some circumstances, this can be beneficial to animals, as demonstrated by taxol, which is commonly used as a cancer medication. License Info. Image Use. Learn how microtubules, actin filaments, and intermediate filaments organize the cell. Comments Close. The Comment you have entered exceeds the maximum length. Submit Cancel. Comments Please Post Your Comment. No comments yet. Save Note Note. Save Cancel Delete. Next Prev Close Edit Delete.

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